Electrochemical Anode Behavior of α-FeSi2 co-Sintered with Solid Electrolyte (Supporting Information)

It is essential in the production of the next generation of rechargeable batteries to elucidate the reaction phases formed after co-sintering in all-solid-state batteries with oxide solid electrolytes and silicon materials and their electrochemical behavior. Herein, we explore the presence or absence of reaction phases and the charge/discharge behavior after co-sintering with the solid electrolyte Li1.5Al0.5Ge1.5(PO4)3 (LAGP) and various silicon active anode materials. In the co-sintering investigation of LAGP and silicon active anode materials, α-FeSi2 do not react with LAGP and the electronic conductivity of α-FeSi2 is maintained even after sintering. In addition, using a mixed sintered sheet consisting of α-FeSi2, solid electrolyte LAGP, and carbon additive vapor-grown carbon fiber, a charge/discharge test is performed at 105 °C for the cell with a Li metal counter electrode and polymer electrolyte. The results of X-ray diffraction measurements of the disassembled test cell after charging/discharging confirm that the reduction decomposition reaction proceeding and disappearing of LAGP phase completely when Li is inserted into the active anode material for the first time. However, when Li is further inserted, Li alloy phases, Li22Si5, and Li22Ge5 appear, and they show reversible charge/discharge behavior of 400 mA h g−1. This is presumed to be owing to the partial reduction of α-FeSi2 to Si and the reduction decomposition of LAGP to produce Ge during the Li insertion process, followed by the formation of Li alloy phases with Li and Si or Ge. Furthermore, while the solid electrolyte LAGP disappear during the first Li insertion, the formation of a Li4SiO4 phase with a broad peak is observed, suggesting that the Li4SiO4 phase might function as a Li conductor.

在下一代可充电电池的生产过程中，阐明在氧化物固态电解质和硅材料全固态电池中，经共烧结形成的反应相及其电化学行为至关重要。本研究旨在探究共烧结固体电解质Li1.5Al0.5Ge1.5(PO4)3（LAGP）和多种硅活性正极材料后，反应相的存在与否以及充放电行为。在LAGP与硅活性正极材料的共烧结研究中，α-FeSi2不与LAGP发生反应，且α-FeSi2的电子导电性在烧结后仍得以保持。此外，采用由α-FeSi2、固体电解质LAGP和碳添加剂气相生长碳纤维混合烧结的烧结片，对配备锂金属对电极和聚合物电解质的电池在105°C下进行充放电测试。对充放电后拆卸的测试电池进行的X射线衍射测量结果表明，在首次向活性正极材料插入锂时，LAGP相的还原分解反应进行并完全消失。然而，当进一步插入锂时，出现了锂合金相Li22Si5和Li22Ge5，它们表现出400 mA h g−1的可逆充放电行为。这被认为是在锂插入过程中，α-FeSi2部分还原为Si，LAGP还原分解产生Ge，随后与Li和Si或Ge形成锂合金相所致。此外，尽管固体电解质LAGP在首次锂插入过程中消失，但观察到形成了具有宽峰的Li4SiO4相，这表明Li4SiO4相可能作为锂导体发挥作用。